A combine is an agricultural vehicle used in the harvesting of crops. The combine is typically self-propelled and is comprised of a forward header assembly and an aft drive and processing section. The header assembly typically is substantially wider than the aft portion of the combine and includes a plurality of spaced corn or row crop heads which are adapted for engaging the crops and removing the grain therefrom. The thus removed grain, in combination with crop residue such as husks in the case of corn harvesting, is then automatically delivered to the aft drive and processing section of the combine. In addition to housing the source of propulsion, such as a diesel engine and operator controls, the aft portion of the combine also includes a complicated threshing system for further separating the grain from the crop residue and for off-loading the thus separated grain from the combine into a transport vehicle such as a truck. The crop residue is then exhausted from an aft portion of the combine and deposited in the field being harvested.
The threshing system includes many stages for separating the grain from the husk or leafy portion of the plant. An early stage of the threshing system typically includes a rotating cylinder operating in conjunction with a concave structure positioned adjacent to and below the cylinder to initiate grain-crop residue separation. The thus separated grain is then subjected to additional processing for further separation, while the crop residue, or chaff, is exhausted from the combine.
The additional processing to which the grain is subjected typically includes a vibrating sieve arrangement upon which the grain and chaff mixture is deposited by the cylinder. This sieve-like structure, frequently referred to as a "straw walker", agitates the mixture, loosens the grain from the chaff, and moves the chaff to the rear of the combine for discharge into the field while allowing the grain to fall under the influence of gravity to a lower portion of the combine. Because the grain and chaff are frequently discharged from the aforementioned cylinder and concave combination onto the straw walkers in a thick, mat-like mass, this mass must be thoroughly agitated in a rather violent manner to remove the grain from the chaff which tends to ball up into a rather dense mass. The mass of chaff and grain has an even greater density and is more difficult to separate in wet conditions. Failure to separate the grain from the chaff results in the grain also being discharged back onto the field which is, of course, wasteful and inefficient.
The present invention addresses the aforementioned limitations of the prior art by providing a straw walker for separating chaff from grain in a combine which provides increased agitation of the chaff and grain mixture as well as increased speed with which the chaff is moved to the rear of the combine for improved separation of the grain from the chaff.